Chemistry Lab equipments: How to use a Buret

One of the most important pice of equipment/glassware used in a chemistry lab is a Buret and it is important that a student know a proper way to use a Buret. Here is a step by step instructions on how to use a Buret with pictures. Please, feel free to share your comments:

Using a Buret
		To fill a buret, close the stopcock at the bottom and use a funnel. You may need to lift up on the funnel slightly, to allow the solution to flow in freely.
		You can also fill a buret using a disposable transfer pipet. This works better than a funnel for the small, 10 mL burets. Be sure the transfer pipet is dry or conditioned with the titrant, so the concentration of solution will not be changed. Before titrating, condition the buret with titrant solution and check that the buret is flowing freely. To condition a piece of glassware, rinse it so that all surfaces are coated with solution, then drain. Conditioning two or three times will insure that the concentration of titrant is not changed by a stray drop of water.
		Check the tip of the buret for an air bubble. To remove an air bubble, whack the side of the buret tip while solution is flowing. If an air bubble is present during a titration, volume readings may be in error.
Rinse the tip of the buret with water from a wash bottle and dry it carefully. After a minute, check for solution on the tip to see if your buret is leaking. The tip should be clean and dry before you take an initial volume reading.
When your buret is conditioned and filled, with no air bubbles or leaks, take an initial volume reading. A buret reading card with a black rectangle can help you to take a more accurate reading. Read the bottom of the meniscus. Be sure your eye is at the level of meniscus, not above or below. Reading from an angle, rather than straight on, results in a parallax error.
		Deliver solution to the titration flask by turning the stopcock. The solution should be delivered quickly until a couple of mL from the endpoint.
The endpoint should be approached slowly, a drop at a time. Use a wash bottle to rinse the tip of the buret and the sides of the flask. Your TA can show you how to deliver a partial drop of solution, when near the endpoint.

Chemistry lab equipments: Glasswares used in chemistry Labs

We have heard from many people about how useful the list of common chemistry lab equipments with pictures have been. In an effort to provide more information about common equipments used in chemistry abs, we have put together a list of common glasswares used in a chemistry labs with pictures and descriptions in this post. Please, let us know if we are missing anything or of you have any questions.

Buret

A buret is used to deliver solution in precisely-measured, variable volumes. Burets are used primarily for titration, to deliver one reactant until the precise end point of the reaction is reached. Click here for instructions on how to use a Buret

Erlenmeyer Flasks and Beakers

Erlenmeyer flasks and beakers are used for mixing, transporting, and reacting, but not for accurate measurements. The volumes stamped on the sides are approximate and accurate to within about 5%.

Graduated Cylinders

Graduated cylinders are useful for measuring liquid volumes to within about 1%. They are for general purpose use, but not for quantitative analysis. If greater accuracy is needed, use a pipet or volumetric flask. Pipet A pipet is used to measure small amounts of solution very accurately. A pipet bulb is used to draw solution into the pipet. Repipet A repipet is a hand operated pump that dispenses solution. Its volumes are accurate to within about 2%. If you need a more precise volume measurement, remeasure at your bench using a more precise piece of glassware, like a graduated cylinder, pipet, or buret.

Volumetric Flask
		A volumetric flask is used to make up a solution of fixed volume very accurately. This volumetric flask measures 500 mL ± 0.2 mL. This is a relative uncertainty of 4 x 10-4 or 400 parts per million. To make up a solution, first dissolve the solid material completely, in less water than required to fill the flask to the mark.
		After the solid is completely dissolved, very carefully fill the flask to the 500 mL mark. Move your eye to the level of the mark on the neck of the flask and line it up so that the circle around the neck looks like a line, not an ellipse. Then add distilled water a drop at a time until the bottom of the meniscus lines up exactly with the mark on the neck of the flask. Take care that no drops of liquid are in the neck of the flask above the mark.
		After the final dilution, remember to mix your solution thoroughly, by inverting the flask and shaking.